The World Wide Web ("Web") has become a very successful means of communication between central sites connected to the Internet and individual users on the Internet who wish to communicate with the site. The communications are controlled by two programs, a Web Browser that runs on the user's computer and a Web server that runs on the site's computer. A Web Browser sends a request to a Web server using the HTTP protocol. A request results in a MIME ("Multipurpose Internet Mail Extensions"--see IETF RFC1341, 1342, 1521) Stream being sent back to the Web Browser. This protocol for communications has become the dominant method for transferring data over wide area networks.
A very popular Web Server can quickly become overloaded. The performance of a server is determined by the processing power of the computer and the network bandwidth available to the server. Sooner or later one of these factors results in requests backing up in a queue waiting to be serviced. Normally, the requests are serviced in a simple first-in, first-out (FIFO) order.
Unfortunately, with FIFO ordering, large jobs can occupy various server resources for long periods of time, delaying short jobs. A limited number of short jobs, on the other hand, will not significantly delay long jobs, since they have much shorter service times.
In a scheduling system based on the amount of system resources needed to fill each request, the smaller jobs would be inserted ahead of the larger job. Unfortunately, a resource based scheduling system of this type can easily "starve" a large job, since the large job can be pre-empted for an indefinite period of time if additional small jobs arrive before it is started.
The above described simple scheduling algorithms do not take into account other scheduling problems. For example, in some network protocols, a block of requests are received by the server and must be serviced in order. In such systems, the server is free to interleave other jobs in the sequence of requests. The above simple scheduling algorithms do not provide an effective method for handling this type of "ordered" request.
Broadly, it is the object of the present invention to provide an improved scheduling method for use by network servers.
It is a further object of the present invention to provide a scheduling method that allows the server to provide a scheduling priority that takes into account both the time of arrival of a request and the system resources needed to fill that request.
It is yet another object of the present invention to provide a scheduling method that allows ordered requests to be processed with non-ordered requests.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.